A titular see in Cilicia Secunda, suffragan to Anazarba. Rhosus or Rhossus was a seaport situated on the Gulf of Issus, now Alexandretta, southwest of Alexandria (Iskenderoun or Alexandretta). It is mentioned by Strabo (XIV, 5; XVI, 2), Ptolemy (V, 14), Pliny (V, xviii, 2), who place it in Syria, and by Stephanus Byzantius; later by Hierocles (Synecd. 705, 7), and George of Cyprus (Descriptio orbis romani, 827), who locate it in Cilicia Secunda. Towards 200, Serapion of Antioch composed a treatise on the Gospel of Peter for the faithful of Rhosus who had become heterodox on account of that book (Eusebius, "Hist. eccl.", VI, xii, 2). Theodoret (Philoth. Hist., X, XI), who places it in Cilicia, relates the history of the hermit Theodosius of Antioch, founder of a monastery in the mountain near Rhosus, who was forced by the inroads of barbarians to retire to Antioch, where he died and was succeeded by his disciple Romanus, a native of Rhosus; these two religious are honoured by the Greek Church on 5 and 9 February. Six bishops of Rhosus are known (Le Quien, "Or. Christ.", II, 905): Antipatros, at the Council of Antioch, 363; Porphyrius, a correspondent of St. John Chrysostom; Julian, at the Council of Chalcedon, 451; a little later a bishop (name unknown), who separated from his metropolitan to approve of the reconciliation effected between John of Antioch and St. Cyril; Antoninus, at the Council of Mopsuestra, 550; Theodore, about 600. The see is mentioned among the suffragans of Anazarba in "Notitiæ episcopatuum" of the Patriarchate of Antioch, of the sixth century (Vailhé in "Echos d'Orient", X, 145) and one dating from about 840 (Parthey, "Hieroclis synecd. et notit. gr. episcopat.", not. Ia, 827). In another of the tenth century Rhosus is included among the exempt sees (Vailhé, ibid 93 seq.). In the twelfth century the town and neighbouring fortress fell into the hands of the Armenians; in 1268 this castle was captured from the Templars by Sultan Bibars (Alishan, "Sissouan", Venice, 1899, 515). Rhosus is near the village of Arsous in the vilayet of Adana.